Reactive mixture for coating molded objects by means of reaction injection molding and coated molded object

ABSTRACT

A reactive mixture for coating mouldings by means of reaction injection moulding, containing at least 40% by weight of (meth)acrylates having at least two double bonds. The reactive mixture contains at least one photoinitiator and at least one thermal initiator. The present invention furthermore describes a coated moulding including a moulding which is obtainable by injection moulding processes and includes at least one polymer selected from polymethyl methacrylate, polymethylmethacrylimide, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer and polymethyl methacrylate copolymers, and a coating which is obtainable by polymerization of (meth)acrylates having at least two double bonds. The coating has an adhesive strength rating of not more than 1 according to the cross hatch test and a decrease in gloss at 20° after a scratch resistance test according to ASTM 1044 (12/05) (applied weight 500 g, number of cycles=100) of not more than 10%.

The present invention relates to a reactive mixture for coatingmouldings by means of reaction injection moulding. Furthermore, thepresent invention describes a coated moulding.

Thermoplastic moulding materials which may be based, for example, onpolymethyl methacrylate (PMMA) are used for a very wide range ofapplications. For this purpose, the materials are extruded or injectionmoulded to give shaped articles.

The shaped articles are widely used nowadays for the production of partssubjected to high stress, such as, for example, displaceable parts(interior and exterior of automobiles, coverings of electronic devices,such as mobile phone, computer, organizer, MP3 player or televisioncoverings), opaque coloured add-on parts (e.g. in the automotiveindustry: exterior mirrors, pillar claddings, mirror triangles) oropaque coloured commodity articles. Owing to the high stress, thesurface of the shaped articles thus used tends to form scratches, whichare often visually unacceptable. Mouldings which were produced byinjection moulding are particularly scratch-sensitive in this respect.Furthermore, from economic points of view, the colour of the mouldingsproduced can be varied only with very great difficulty, in order thus topermit simple colour matching of the add-on part with the respectiveautomobile, for example during production.

For improving the scratch resistance and for colour matching, themouldings described above can be provided with finish coats. However,the classical application of reactive finishes is relatively complicatedand therefore expensive. These processes are scarcely suitable for theproduction of mass-produced articles.

For this reason, processes by means of which a scratch-resistant layercan be applied to the mouldings relatively economically by means ofinjection moulding processes have already been developed. For example,the publications JP 11300776 and JP 2005074896 describe injectionmoulding processes in which a moulding having a scratch-resistant layeris obtained.

The publication JP 11300776 (Dainippon Toryo, 1998) describes atwo-stage RIM process. First, a moulding is obtained by metathesis RIMof dicyclopentadiene. After the curing, the movable part of the RIMmould is retracted so that a defined gap forms between moulding andmould. A coating material which consists of acrylate-functionalizedurethane oligomers, styrene, diacrylate crosslinking agents andoptionally fillers and pigments (TiO₂, talc) and is cured by a freeradical method at 95° C. for 2 min is injected into this gap in a secondRIM process.

The document JP 2005074896 (Toyota Motor Corp.; Dainippon Toryo Co.)likewise describes an RIM process. In a first conventional injectionmoulding step, a plastic, in particular polycarbonate (PC), is processedto give a sheet-like shaped article. The mould then opens to form asmall gap and, within a few seconds, a reactive solution ofacrylate-functionalized urethane oligomers, acrylate crosslinkingagents, inhibitors and an organic peroxide initiator is injected andcured. At 95° C., the curing is complete after a few seconds and thecomposite body is removed from the mould after 90 s. It has good scratchresistance, adhesion of the composite, thermal shock resistance andresistance to warm water cycling. The presence of a urethane oligomerwhich is composed of isophorone diisocyanate orbis(isocyanocyclohexyl)methane building blocks is essential in allclaims.

The mouldings described above already have good properties. However,attempts are continuously being made to improve the scratch resistanceof mouldings thus obtained. Furthermore, the production istime-consuming so that the overall process is expensive. In addition,the stability of the mouldings to weathering is in need of improvement.Premature polymerization of the reactive mixture in the injectionmoulding apparatus presents a further problem of the injection mouldingprocess described in publications JP 11300776 and JP 2005074896, so thatshort cycle times are scarcely achievable by these processes in massproduction.

In view of the prior art, it was the object of the present invention toprovide a reactive mixture for coating mouldings by means of a reactioninjection moulding, which mixture leads to a coating having particularlyhigh scratch resistance and high adhesive strength on a moulding.

A further object of the invention was to provide a reactive mixturewhich can be completely cured particularly easily and in a short time.

In addition, it was an object of the present invention to provideprocesses for the production of coated mouldings which can be carriedout easily and economically. The moulding should be obtained therebywith cycle times as short as possible and, as a whole, with littleenergy consumption.

The provision of mouldings having outstanding mechanical properties wasfurthermore an object of the present invention. In particular, themouldings should show a high scratch resistance and great hardness.Moreover, the coated mouldings should have high resistance to weatheringand to chemicals.

These objects and further objects which are not explicitly mentioned butcan be derived or deduced directly from the relationships discussed hereat the outset are achieved by a reactive mixture having all features ofpatent claim 1. Modifications of the reactive mixture according to theinvention are protected in the dependent claims relating back to claim1. With regard to the process and the moulding, claims 18 and 27 provideachievements of the underlying object.

The present invention accordingly relates to a reactive mixture forcoating mouldings by means of reaction injection moulding, comprising atleast 40% by weight of (meth)acrylates having at least two double bonds,which is characterized in that the reactive mixture comprises at leastone photoinitiator and at least one thermal initiator.

It is possible thereby in an unforeseeable manner to provide a coatedmoulding which has outstanding scratch resistance and can be obtainedvery economically. Surprisingly, the coating shows a very high adhesivestrength in the moulding. In addition, the coatings obtained with thereactive mixture according to the invention show high stability toweathering. Furthermore, the coated mouldings have good mechanicalproperties and may exhibit both particularly great hardness and goodimpact strength.

Furthermore, the reactive mixture according to the invention permits theproduction of a coating resistant to chemicals and to heat on amoulding.

Moreover, the reactive mixture may have additives in order to adapt thedesired properties to specific requirements. Thus, colour matching ofthe moulding may be effected in a simple manner.

Furthermore, the process according to the invention can be carried outeasily and economically, it being possible to obtain the moulding withsurprisingly short cycle times and, as a whole, with little energyconsumption.

The reactive mixture according to the invention has at least 40% byweight, preferably at least 60% by weight and particularly preferably atleast 90% by weight of (meth)acrylates having at least two double bonds,based on the total weight of the reactive mixture. The term “doublebond” designates in particular carbon-carbon double bonds which arecapable of free radical polymerization. The expression “(meth)acrylate”represents acrylate, methacrylate and mixtures of the two.(Meth)acrylates having at least two double bonds are also known ascrosslinking monomers. These include in particular (meth)acrylateshaving two double bonds such as, for example, (meth)acrylates which arederived from unsaturated alcohols, such as, for example, 2-propynyl(meth)acrylate, allyl (meth)acrylate or vinyl (meth)acrylate, and(meth)acrylates which are derived from diols or higher hydric alcohols,such as, for example, glycol di(meth)acrylates, such as ethylene glycoldi(meth)acrylate, diethylene glycol di(meth)-acrylate, triethyleneglycol di(meth)acrylate, tetra- and polyethylene glycoldi(meth)acrylate, 1,3-butane-diol (meth)acrylate, 1,4-butanediol(meth)acrylate, 1,6-hexanediol di(meth)acrylate, glyceryldi(meth)-acrylate and diurethane dimethacrylate; (meth)acrylates havingthree or more double bonds, such as, for example, glyceryltri(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythrityltetra(meth)acrylate and dipentaerythrityl penta(meth)acrylate.Particularly preferred (meth)acrylates having at least two double bondsare in particular 1,6-hexanediol diacrylate, trimethylolpropanetriacrylate, pentaerythrityl tetra-acrylate and dipentaerythritylpentaacrylate.

According to a particular modification, the reactive mixture maycomprise at least one (meth)acrylate having three or more double bonds.Preferably, the proportion of (meth)acrylates having three or moredouble bonds is at least 10% by weight, particularly preferably at least25% by weight, especially preferably at least 50% by weight and veryparticularly preferably at least 90% by weight, based on the weight ofthe reactive mixture.

Reactive mixtures which comprise not more than 90% by weight,particularly preferably not more than 75% by weight, especiallypreferably not more than 50% by weight and very particularly preferablynot more than 7% by weight of monomers having two or less double bondsare furthermore of particular interest.

According to a particular embodiment, the reactive mixture preferablycomprise 1,6-hexanediol diacrylate, trimethylolpropane triacrylateand/or pentaerythrityl tetraacrylate. In particular, reactive mixtureswhich comprise trimethylolpropane triacrylate and penta-erythrityltetraacrylate are of particular interest, it being possible for theweight ratio of trimethylol-propane triacrylate to pentaerythrityltetraacrylate to be preferably in the range of 10:1 to 1:10, preferablyin the range of 5:1 to 1:5, particularly preferably in the range of 3:1to 1:3 and very particularly preferably in the range of 2:1 to 1:2.

According to a further development, the reactive mixture preferablycomprises trimethylolpropane triacrylate and 1,6-hexanediol diacrylate,it being possible for the weight ratio of trimethylolpropane triacrylateto 1,6-hexanediol diacrylate preferably to be in the range of 10:1 to1:10, preferably in the range of 5:1 to 1:5, particularly preferably inthe range of 3:1 to 1:3 and very particularly preferably in the range of2:1 to 1:2.

Reactive mixtures which preferably comprise pentaerythrityltetraacrylate and 1,6-hexanediol diacrylate are furthermore ofparticular interest. Expediently, the weight ratio of pentaerythrityltetraacrylate to 1,6-hexanediol diacrylate may be in the range of 10:1to 1:10, preferably in the range of 5:1 to 1:5, particularly preferablyin the range of 3:1 to 1:3 and very particularly preferably in the rangeof 2:1 to 1:2.

Reactive mixtures which comprise pentaerythrityl tetraacrylate and/ortrimethylolpropane triacrylate surprisingly show particularly highscratch resistance which increases in particular with the proportion ofpentaerythrityl tetraacrylate. Reactive mixtures which comprise1,6-hexanediol diacrylate and/or trimethylol-propane triacrylate showparticularly high UV stability which can be determined in particular bythe xenon arc test. Thus, mixtures having a high proportion of1,6-hexanediol diacrylate retain high scratch resistance according tothe abrasive disc test even after xenon arc exposure.

The scratch resistance of the coating is dependent, inter alia, on thenumber of polymerizable double bonds, based on the weight of themixture. The higher this proportion, the higher is the scratchresistance which the coating can achieve. Preferably, the reactivemixture can accordingly have at least 1 mol of double bond per 120 g ofreactive mixture, particularly preferably at least 1 mol of double bondper 105 g of reactive mixture. The scratch resistance can be increasedthereby, in particular by using (meth)acrylates having three or moredouble bonds.

The reactive mixture can be used in particular in reactive injectionmoulding processes. Accordingly, the mixture has a viscosity whichpermits such use. Preferably, the dynamic viscosity of the reactivemixture is in the range of 1 to 200 mPa·s at 25° C., particularlypreferably in the range of 5 to 50 mPa·s at 25° C., it being possible todetermine the dynamic viscosity according to Brookfield (with ULadaptor).

For curing, the reactive mixture comprises at least one initiator bymeans of which the monomers can be subjected to free radicalpolymerization. Thermal initiators which form free radicals by theaction of heat or photoinitiators which initiate free radicalpolymerization on irradiation with electromagnetic waves can be usedhere. Surprisingly, particular advantages can be achieved by usingreactive mixtures which comprise both thermal initiators andphoto-initiators. These advantages include in particular short cycletimes in the production of the coated mouldings, particularly highstability to weathering, scratch resistance and adhesive strength of thecoating.

Suitable thermal initiators are, inter alia, azo compounds, peroxycompounds, persulphate compounds or azoamidines. Nonlimiting examplesare dibenzoyl peroxide, dicumene peroxide, cumene hydroperoxide,diisopropyl peroxydicarbonate, bis(4-tert-butylcyclo-hexyl)peroxydicarbonate, dipotassium persulphate, ammonium peroxydisulphate,2,2′-azobis(2-methylpropio-nitrile) (AIBN), 2,2′-azobis(isobutyramidine)hydro-chloride, benzpinacol, dibenzyl derivatives, methyl ethyleneketone peroxide, 1,1-azobiscyclohexanecarbo-nitrile, methyl ethyl ketoneperoxide, acetylacetone peroxide, dilauryl peroxide, didecanoylperoxide, tert-butyl per-2-ethylhexanoate, ketone peroxide, methylisobutyl ketone peroxide, cyclohexanone peroxide, dibenzoyl peroxide,tert-butyl peroxybenzoate, tert-butyl peroxyisopropylcarbonate,2,5-bis(2-ethyl-hexanoylperoxy)-2,5-dimethylhexane, tert-butylperoxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethyl-hexanoate,tert-butyl peroxyisobutyrate, tert-butyl peroxyacetate, dicumylperoxide, 1,1-bis(tert-butyl-peroxy)cyclohexane,1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, cumylhydroperoxide, tert-butyl hydroperoxide, bis(4-tert-butylcyclohexyl)peroxy-dicarbonate, and the free radical formers obtainable from DuPontunder the name ®Vazo, for example ®Vazo V50 and ®Vazo WS.

Expediently, the reactive mixture may comprise 0.01% by weight to 3% byweight, preferably 0.1% by weight to 2.5% by weight and particularlypreferably 0.5% by weight to 1.5% by weight of thermal initiator, basedon the weight of the reactive mixture.

The preferred photoinitiators include, inter alia,α,α-diethoxyacetophenone (DEAP, Upjohn Corp.), n-butyl-benzoin ether(®Triganol-14, AKZO) and 2,2-dimethoxy-2-phenylacetophenone (®Irgacure651) and 1-benzoylcyclo-hexanol (®Irgacure 184),bis(2,4,6-trimethylbenzoyl)-phenylphospine oxide (®Irgacure 819) and1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-phenylpropan-1-one (®Irgacure2959), which in each case are commercially available from Ciba GeigyCorp.

The proportion of photoinitiator is not critical per se. Preferably, thereactive mixture has 0.01% by weight to 10% by weight, particularlypreferably 0.3% by weight to 5% by weight and very particularlypreferably 0.7% by weight to 2.3% by weight of photoinitiator, based onthe weight of the reactive mixture.

According to a preferred modification, the weight ratio ofphotoinitiator to thermal initiator may be in the range of 20:1 to 1:5,preferably in the range 15:1 to 1:1 and particularly preferably in therange 10:1 to 2:1.

In addition to the abovementioned constituents, the reactive mixture maycomprise a lubricant. Surprisingly, this makes it possible to improvethe demouldability of the coated moulding without reducing the adhesivestrength to critical values. Accordingly, lubricants, for exampleselected from the group consisting of the polysiloxanes, the saturatedfatty acids having less than C₂₀, preferably C₁₆ to C₁₈, carbon atoms orthe saturated fatty alcohols having less than C₂₀, preferably C₁₆ toC₁₈, carbon atoms may be present as auxiliaries. Small proportions ofnot more than 0.25, e.g. 0.05 to 0.2, % by weight, based on the weightof the reactive mixture, are preferably present. For example, stearicacid, palmitic acid and industrial mixtures of stearic and palmitic acidare suitable. In addition, polysiloxanes which are acrylated, such as,for example, 13/6/αω2-hexylacryloylsiloxane are expedient, it beingpossible to obtain this compound, for example, under the tradename RC725 from Goldschmidt GmbH. Polysiloxanes can also be used in largeamounts. For example, proportions of not more than 10% by weight,preferably of not more than 1% by weight and very particularlypreferably of not more than 0.5% by weight are expedient. For example,n-hexadecanol, n-octadecanol and industrial mixtures of n-hexadecanoland n-octadecanol are furthermore suitable. A particularly preferredlubricant or mould release agent is stearyl alcohol.

Furthermore, the reactive mixture may comprise customary additives, suchas colorants, pigments, for example metallic pigments, UV stabilizers,fillers or nanomaterials, in particular ITO nanoparticles. Theproportion of these additives is dependent on the intended use and maytherefore be within wide ranges. This proportion, if additives arepresent, may preferably be 0 to 30% by weight, particularly preferably0.1 to 5% by weight.

The reactive mixture provided by the present invention can be used inparticular for coating mouldings by means of reaction injectionmoulding. Accordingly, the present invention also relates to processesfor the production of coated mouldings.

Injection moulding processes have long been known and are widely used.In general, the moulding material is injected into an injection mouldand cooled to give a moulding. The moulding thus obtained can then beprovided with a coating.

For example, the shaped article thus obtained can be finally cooled andremoved from the mould. In a second, downstream separate injectionmoulding step, for example, this preform is then placed in ortransferred to another mould having a created cavity and the reactivemixture is injected into the mould and thus injected onto the preform.This process is known as the insert or transfer process. For thesubsequently achievable adhesion, it is particularly advantageous if thepreformed shaped article is preheated.

According to a preferred embodiment, the coating is advantageouslyeffected in particular by changing the injection mould, a space formingbetween that surface of the moulding which is to be coated and the innersurface of the injection mould. The resulting space can be filled with areactive mixture by injection moulding. The reactive mixture canpreferably first be thermally cured and, after the thermal curing, curedby irradiation.

By means of this procedure, it is possible to obtain in particularcoated mouldings having high scratch resistance, the coating havingparticularly good adhesive strength. Moreover, particularly short cycletimes can also be achieved.

Plants which permit such a procedure are described, inter alia, in thedocuments JP 11300776 and JP 2005074896 described above.

Moulding materials for the production of the moulding to be coated areknown per se, these moulding materials containing thermoplasticallyprocessable polymers as an obligatory component. The preferred polymersinclude, for example, poly(meth)acrylates, in particular polymethylmethacrylate (PMMA), poly(meth)acrylamides, polyacrylonitriles,polystyrenes, polyethers, polyesters, polycarbonates and polyvinylchlorides. Poly(meth)acrylates and poly(meth)acrylimides are preferredhere. These polymers can be used individually or as mixture.Furthermore, these polymers may also be present in the form ofcopolymers. Preferred copolymers are, inter alia, styrene-acrylonitrilecopolymers, styrene-maleic acid copolymers and polymethyl methacrylatecopolymers, in particular polymethyl methacrylate-poly(meth)acrylimidecopolymers.

Particularly preferred moulding materials have at least 15% by weight,preferably at least 50% by weight and particularly preferably at least80% by weight of polymethyl methacrylate, polymethylmethacrylimideand/or polymethyl methacrylate copolymers, based on the total weight ofthe moulding material.

The moulding materials of the present invention can preferably containpoly(meth)acrylates. The expression (meth)acrylates comprisesmethacrylates and acrylates and mixtures of the two.

Poly(meth)acrylates are polymers which are obtainable by polymerizationof a monomer mixture which has at least 60% by weight, preferably atleast 80% by weight, of (meth)acrylates, based on the weight of themonomers. These monomers are widely known among those skilled in the artand are commercially available. They include, inter alia, (meth)acrylicacid and (meth)acrylate which are derived from saturated alcohols, suchas methyl (meth)acrylate, ethyl (meth)-acrylate, propyl (meth)acrylate,butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate,2-ethyl-hexyl (meth)acrylate, heptyl (meth)acrylate; (meth)-acrylateswhich are derived from unsaturated alcohols, such as, for example, oleyl(meth)acrylate, 2-propynyl (meth)acrylate, allyl (meth)acrylate, vinyl(meth)acrylate, etc; amides and nitriles of (meth)acrylic acid, such asN-(3-dimethylaminopropyl)(meth)acrylamide,N-(diethylphosphono)(meth)acrylamide,1-methacryloylamido-2-methyl-2-propanol; cycloalkyl (meth)acrylates,such as 3-vinylcyclohexyl (meth)acrylate, bornyl (meth)-acrylate;hydroxyalkyl (meth)acrylates, such as 3-hydroxypropyl (meth)acrylate,3,4-dihydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate,2-hydroxypropyl (meth)-acrylate; glycol di(meth)acrylates, such as1,4-butanediol (meth)acrylate, (meth)acrylates of ethyl alcohols, suchas tetrahydrofurfuryl (meth)acrylate, vinyloxyethoxyethyl(meth)acrylate; and polyfunctional (meth)acrylates, such astrimethylolpropane tri(meth)acrylate.

In addition to the (meth)acrylates described above, further unsaturatedmonomers which are copolymerizable with the abovementioned methacrylatescan also be used for the preparation of the poly(meth)acrylates. Ingeneral, these compounds are used in an amount of 0 to 40% by weight,preferably 0 to 20% by weight, based on the weight of the monomers, itbeing possible to use the comonomers individually or as a mixture.

These include, inter alia, 1-alkenes, such as 1-hexene, 1-heptene;branched alkenes, such as, for example, vinylcyclohexane,3,3-dimethyl-1-propene, 3-methyl-1-diisobutylene, 4-methyl-1-pentene;vinyl esters, such as vinyl acetate; styrene, substituted styreneshaving an alkyl substituent in the side chain, such as, for example,α-methylstyrene and α-ethylstyrene, substituted styrenes having an alkylsubstituent on the ring, such as vinyltoluene and p-methylstyrene,halogenated styrenes such as, for example, monochlorostyrenes,dichlorostyrenes, tribromostyrenes and tetrabromostyrenes; heterocyclicvinyl compounds, such as 2-vinylpyridine, 3-vinylpyridine,2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine,2,3-dimethyl-5-vinylpyridine, vinyl-pyrimidine, vinylpiperidine,9-vinylcarbazole, 3-vinyl-carbazole, 4-vinylcarbazole, 1-vinylimidazole,2-methyl-1-vinylimidazole, N-vinylpyrrolidone, 2-vinyl-pyrrolidone,N-vinylpyrrolidine, 3-vinylpyrrolidine, N-vinylcaprolactam,N-vinylbutyrolactam, vinyloxolane, vinylfuran, vinylthiophene,vinylthiolane, vinyl-thiazoles and hydrogenated vintylthiazoles,vinyl-oxazoles and hydrogenated vinyloxazoles; vinyl and isoprenylether;

maleic acid derivatives, such as, for example, maleic anhydride,methylmaleic anhydride, maleimide, methylmaleimide; anddienes, such as, for example, divinylbenzene.

Preferred poly(meth)acrylates are obtainable by polymerization ofmixtures which have at least 20% by weight, in particular at least 60%by weight and particularly preferably at least 80% by weight, based ineach case on the total weight of the monomers to be polymerized, ofmethyl methacrylate. In the context of the present invention, thesepolymers are referred to as polymethyl methacrylates. Preferred mouldingmaterials may contain different poly(meth)acrylates which differ, forexample, in the molecular weight or in the monomer composition.

The preparation of the (meth)acrylate homo- and/or copolymers from themonomers described above by the various free radical polymerizationprocesses is known per se. Thus, the polymers can be prepared by mass,solution, suspension or emulsion polymerization. The mass polymerizationis described by way of example in Houben-Weyl, volume E20, part 2(1987), page 1145 et seq. Information regarding the solutionpolymerization is also to be found there on page 1156 et seq.Explanations of the suspension polymerization technique are also to befound there on page 1149 et seq., while the emulsion polymerization isalso elaborated on and explained there on page 1150 et seq.

Furthermore, preferred moulding materials may comprisepoly(meth)acrylimides. Poly(meth)acrylimides have repeating units whichcan be represented by the formula (I)

in which R¹ and R² are identical or different and denote hydrogen or amethyl group and R³ denotes hydrogen or an alkyl or aryl radical havingup to 20 carbon atoms.

Units of the structure (I) preferably form more than 30% by weight,particularly preferably more than 50% by weight and very particularlypreferably more than 80% by weight of the poly(meth)acrylimide.

The preparation of poly(meth)acrylimides is known per se and isdisclosed, for example, in British Patent 1 078 425, British Patent 1045 229, German Patent 1 817 156 (=U.S. Pat. No. 3,627,711) or GermanPatent 27 26 259 (=U.S. Pat. No. 4,139,685).

In addition, these copolymers may contain further monomer units whicharise, for example, from esters of acrylic or methacrylic acid, inparticular with lower alcohols having 1-4 carbon atoms, styrene, maleicacid or the anhydride thereof, itaconic acid or the anhydride thereof,vinylpyrrolidone, vinyl chloride or vinylidene chloride. The proportionof the comonomers, which cannot be cyclized or can be cyclized only withvery great difficulty, should not exceed 30% by weight, preferably 20%by weight and particularly preferably 10% by weight, based on the weightof the monomers.

Moulding materials which can preferably be used are those which comprisepoly(N-methylmethacrylimides) (PMMI) and/or polymethyl methacrylates(PMMA). Poly(N-methylmethacrylimides) (PMMI), polymethyl methacrylates(PMMA) and/or PMMI-PMMA copolymers are preferably copolymers of PMMI andPMMA which are prepared by partial cycloimidization of PMMA. (PMMI whichis prepared by partial imidization of PMMA is usually prepared in such away that not more than 83% of the PMMA used are imidized. The resultingproduct is referred to as PMMI but strictly speaking is a PMMI-PMMAcopolymer.) Both PMMA and PMMI or PMMI-PMMA copolymers are commerciallyavailable, for example under the brand name Pleximid from Röhm. Anexemplary copolymer (Pleximid 8803) has 33% of MMI units, 54.4% of MMAunits, 2.6% of methacrylic acid units and 1.2% of anhydride units. Theproducts and their preparation are known (Hans R. Kricheldorf, Handbookof Polymer Synthesis, Part A, published by Marcel Dekker Inc. NewYork—Basel—Hong Kong, page 223 et seq.; H. G. Elias, Makromoleküle[Macromolecules], published by Hüthig and Wepf Basel—Heidelberg—NewYork; U.S. Pat. Nos. 2,146,209 and 4,246,374).

In addition, the moulding materials may comprise styrene-acrylonitrilepolymers (SAN). Particularly preferred styrene-acrylonitrile polymerscan be obtained by polymerization of mixtures which consist of

70 to 92% by weight of styrene,8 to 30% by weight of acrylonitrile and0 to 22% by weight of further comonomers, based in each case on thetotal weight of the monomers to be polymerized.

For improving the impact strength values, silicone rubber graftcopolymers can be mixed with the moulding materials, which graftcopolymers are composed of

0.05 to 95% by weight, based on the total weight of the copolymer, of acore a) of an organosilicon polymer which corresponds to the generalformula (R₂SiO_(2/2))_(x).(RSiO_(3/2))_(y).(SiO_(4/2))_(z) where x=0 to99.5 mol %, y=0.5 to 100 mol % and z=0 to 50 mol %, R denoting identicalor different alkyl or alkenyl radicals having 1 to 6 carbon atoms, arylradicals or substituted hydrocarbon radicals,0 to 94.5% by weight, based on the total weight of the copolymer, of apolydialkylsiloxane layer b) and5 to 95% by weight, based on the total weight of the copolymer, of ashell c) of organic polymer, the core a) comprising vinyl groups priorto grafting and the shell c) being obtainable by free radicalpolymerization of a mixture which comprises acrylates and methacrylates.

The moulding materials according to the invention can furthermorecontain acrylate rubber modifiers. Surprisingly, outstanding impactstrength behaviour of the mouldings at room temperature (about 23° C.)which were produced from the moulding materials can be achieved thereby.What is particularly important is that the mechanical and thermalproperties, such as, for example, the modulus of elasticity or the Vicatsoftening temperature, are maintained at a very high level. If anattempt is made to achieve similar notched impact strength behaviour atroom temperature only by the use of acrylate rubber modifier or siliconerubber graft copolymer, these values decrease substantially.

Such acrylate rubber modifiers are known per se. They are copolymerswhich have a core-shell structure, the core and the shell having a highproportion of the (meth)acrylates described above.

Preferred acrylate rubber modifiers here have a structure comprising twoshells which differ in their composition.

Particularly preferred acrylate rubber modifiers have, inter alia, thefollowing composition:

-   Core: Polymer having a proportion of methyl methacrylate of at least    90% by weight, based on the weight of the core.-   Shell 1: Polymer having a proportion of butyl acrylate of at least    80% by weight, based on the weight of the first shell.-   Shell 2: Polymer having a proportion of methyl methacrylate of at    least 90% by weight, based on the weight of the second shell.

For example, a preferred acrylate rubber modifier may have the followingcomposition:

-   Core: Copolymer of methyl methacrylate (95.7% by weight), ethyl    acrylate (4% by weight) and allyl methacrylate (0.3% by weight)-   S1: Copolymer of butyl acrylate (81.2% by weight), styrene (17.5% by    weight) and allyl methacrylate (1.3% by weight)-   S2: Copolymer of methyl methacrylate (96% by weight) and ethyl    acrylate (4% by weight)

The ratio of core to shell(s) of the acrylate rubber modifier may varywithin wide ranges. Preferably, the weight ratio of core to shell C/S isin the range of 20:80 to 80:20, preferably of 30:70 to 70:30, in thecase of modifiers having one shell or the ratio of core to shell 1 toshell 2 C/S1/S2 is in the range of 10:80:10 to 40:20:40, particularlypreferably of 20:60:20 to 30:40:30, in the case of modifiers having twoshells.

The particle size of the acrylate rubber modifiers is usually in therange of 50 to 1000 nm, preferably 100 to 500 nm and particularlypreferably 150 to 450 nm, without any limitation being intended thereby.

According to a particular aspect of the present invention, the weightratio of silicone rubber graft copolymer to acrylate rubber modifier isin the range of 1:10 to 10:1, preferably of 4:6 to 6:4.

Particular moulding materials consist of

-   f1) 20 to 95% by weight of poly(meth)acrylates,-   f2) 0 to 45% by weight of styrene-acrylonitrile polymers,-   f3) 5 to 60% by weight of silicone rubber graft copolymers-   f4) 0 to 60% by weight of impact modifiers based on acrylate rubber,    based in each case on the weight of the components f1 to f4,    and customary additives and compounding materials.

In addition, the compositions to be polymerized, the moulding materialsaccording to the invention or the mouldings obtainable therefrom maycontain further widely known additives. These additives include, interalia, molecular weight regulators, release agents, antistatic agents,antioxidants, demoulding agents, flameproofing agents, lubricants, dyes,flow improvers, fillers, light stabilizers, pigments, antiweatheringagents and plasticizers.

The additives are used in customary amounts, i.e. up to 80% by weight,preferably up to 30% by weight, based on the total mass. If the amountis greater than 80% by weight, based on the total mass, properties ofthe plastics, such as, for example, the processability, may bedisturbed.

The weight average molecular weight M_(w) of the homo- and/or copolymersto be used according to the invention as matrix polymers may vary withinwide ranges, the molecular weight usually being tailored to the intendeduse and the method of processing of the moulding material. In general,however, it is in the range between 20 000 and 1 000 000 g/mol,preferably 50 000 to 500 000 g/mol and particularly preferably 80 000 to300 000 g/mol, without any limitation being intended thereby.

The thickness of the coating is often dependent on the type of reactivemixture and the moulding. The production of very thin coatings is oftentechnically very demanding. On the other hand, very thick coatingsfrequently have a strong tendency to cracking, the adhesive strengthdecreasing in some cases. Coated mouldings whose coating preferably hasa thickness in the range of 1 μm to 100 μm, preferably 5 μm to 75 μm,particularly preferably 8 μm to 50 μm, especially preferably 10 μm to 40μm and very particularly preferably 15 μm to 30 μm are therefore ofparticular interest. The thickness of the coating can be adjusted viathe size of the space between that surface of the moulding which is tobe coated and the inner surface of the injection mould.

The temperature at which the moulding material is injected into theinjection mould depends in particular on the type of polymer and of theadditives. These processing temperatures are known to the person skilledin the art. In general, the moulding material is injected into theinjection mould at a temperature in the range of 150 to 350° C.,preferably 220 to 330° C.

The temperature of the mould can also be adjusted to the temperaturecustomary for the respective moulding material. The moulding materialcan preferably be cooled to a temperature in the range of 40 to 160° C.,particularly preferably 70 to 150° C. and very particularly preferably60 to 80° C. before the reactive mixture is injected into the space.

The temperature at which the thermal curing of the reactive mixture iseffected is dependent on the type of thermal initiator. In particular,processes in which the thermal curing is preferably effected at atemperature in the range of 70 to 160° C., preferably 80 to 130° C.,particularly preferably in the range 85 to 120° C. and very particularlypreferably in the range 90 to 110° C. in the injection mould are ofparticular interest. If the temperature during the thermal curing is toohigh, the formation of cracks may occur after UV irradiation. In thecase of temperatures which are too low, the coating often shows anexcessively high adhesion to the metal of the injection mould, it alsobeing possible in some cases to improve the scratch resistance by ahigher temperature during the thermal curing. The ranges described abovehave proved to be particularly expedient, without any limitationintended thereby.

According to a particular embodiment, the reactive mixture can beeffected, for example, at a temperature in the range of 70 to 85° C.,preferably in the range of to 80° C. This embodiment is particularlyadvantageous if the reactive mixture comprises a particularly highproportion of compounds having at least four double bonds, for exampleof pentaerythrityl tetra(meth)acrylate. According to a furtherdevelopment of the process according to the invention, the reactivemixture can be cured at a temperature in the range of 85° C. to 120° C.,preferably in the range of 90° C. to 110° C. This embodiment isparticularly advantageous if the reactive mixture comprises aparticularly high proportion of compounds having two or three doublebonds, such as, for example, 1,6-hexanediol di(meth)-acrylate.

The reactive mixture can be cured at the same temperature at which theinjection moulding is cooled in the mould. The beginning and the rate ofthe polymerization (curing) of the reactive mixture can be adjustedthereby by the choice of the type and of the proportion of thermalinitiator and by the choice of the mould temperature. In addition, thebeginning of curing can be controlled by the choice of thepolyfunctional (meth)acrylates present in the reactive mixture.

After the thermal curing, the precured reactive mixture can be cured byirradiation at a temperature in the range of 0° C. to 120° C.,preferably 10° C. to 40° C. Customary radiation sources can be used forthis purpose, depending on the type of initiator. The curing canpreferably be effected in particular by UV radiation, it being possiblefor the wavelength of the radiation source used to be in particular inthe range of 100 nm to 500 nm, preferably 200 to 400 nm.

The present invention provides in particular novel coated mouldingswhich have an outstanding property profile and can therefore be used fora variety of applications. The present invention accordingly furthermorerelates to coated mouldings comprising a moulding which is obtainable byinjection moulding processes and comprises at least one polymer selectedfrom the group consisting of polymethyl methacrylate,polymethylmethacrylimide, styrene-acrylonitrile copolymer,styrene-maleic acid copolymer and polymethyl methacrylate copolymers anda coating which is obtainable by polymerization of (meth)acrylateshaving at least two double bonds.

The moulding is distinguished in particular by high scratch resistance,which can be determined, for example, by an abrasive disc test.Especially coated, transparent mouldings whose haze value after ascratch resistance test according to ASTM 1044 (12/05) (applied weight500 g, number of cycles=100) increases by not more than 10%,particularly preferably by not more than 6% and very particularlypreferably by not more than 3% are of particular interest. The scratchresistance according to ASTM 1044 (12/05) (applied weight 500 g, numberof cycles=100) can moreover be measured by the decrease in gloss at 20°.Here, preferred coated mouldings show a decrease of gloss at 20° after ascratch resistance test according to ASTM 1044 (12/05) (applied weight500 g, number of cycles=100) of not more than 10%, particularlypreferably by not more than 6% and very particularly preferably by notmore than 3%. The decrease in gloss at 20° C. can be determinedaccording to DIN EN ISO 2813. By determining a change of gloss, forexample, the scratch resistance of coloured mouldings or of colouredcoatings can be measured.

In addition, the mouldings according to the invention show outstandingadhesive strength of the coating which can be investigated according tothe cross hatch test. For this purpose, the coating is scored crosswiseand thus divided into chessboard-like individual segments. In general,at least 20 individual segments, preferably at least 25 individualsegments, are formed thereby. Here, the spacing between the lines isabout 1 mm. A 25 mm wide adhesive tape is then stuck on and peeled offagain. The force required to release the adhesive tape per cm², measuredaccording to DIN EN ISO 2409, is about 10 N per 25 mm width. Forcarrying out the test, for example, an adhesive tape which is obtainableunder the trade name type 4104 from Tesa can be used. The coatedmouldings preferably achieve a rating according to the cross hatch testof not more than 1, particularly preferably of 0. The coated mouldingsachieve a rating of 1 if not substantially more than 5% of theindividual segments are detached. If none of the individual segments(0%) is detached, the coated mouldings achieve a rating of 0.

In addition, preferred coatings are free of cracks and show highresistance to chemicals. Thus, the coatings resist in particularethanol, ethanol/water (70/30), petrol, pancreatin and sulphuric acid(1% strength), no stress cracks being formed through contact with thesecompounds.

Preferred mouldings may have a modulus of elasticity greater than orequal to 1200 MPa, preferably greater than or equal to 1600 MPa,according to ISO 527 (at 1 mm/min). Furthermore, mouldings according tothe invention may exhibit a Charpy impact strength greater than or equalto 10 kJ/m², preferably greater than or equal to 15 kJ/m², according toISO179.

In addition, plastics having tensile strengths greater than or equal to55, preferably greater than or equal to 60, according to DIN 53 455-1-3(at 1 mm/min), can be produced, which plastics have excellent scratchresistance.

It is particularly surprising that this scratch-resistant moulding mayhave a transmittance τ_(D65)≧88%, preferably ≧90%, according to DIN 5036Part 3. No limitation of the invention is intended by the abovementionedmechanical and/or optical properties of the moulding. Rather, these dataserve for illustrating the particularly outstanding properties of themoulding which can be achieved in combination with good scratchresistance.

Furthermore, the mouldings of the present invention may show excellentstability to weathering. Thus, the stability to weathering according tothe xenon arc test is preferably at least 1000 hours, particularlypreferably at least 2000 hours. This stability can be determined, forexample, by a slight decrease of the transmittance or by a slightdecrease of the scratch resistance. Especially coated mouldings whosetransmittance after exposure to a xenon arc for 2000 hours decreases bynot more than 10%, particularly preferably by not more than 5%, based onthe transmittance value at the beginning of the irradiation, are ofparticular interest. In addition, preferred mouldings may show anincrease in the haze value after a scratch resistance test according toASTM 1044 (12/05) (applied weight 500 g, number of cycles=100) to notmore than 25%, particularly preferably to not more than 15%, afterexposure to a xenon arc for 2000 hours. Furthermore, the determinationof the scratch resistance after exposure to a xenon arc is also possiblevia the decrease in the gloss. Here, preferred coated mouldings show adecrease in the gloss at 20° after a scratch resistance test accordingto ASTM 1044 (12/05) (applied weight 500 g, number of cycles=100) of notmore than 25%, particularly preferably by not more than 20% and veryparticularly preferably by not more than 15% after exposure to a xenonarc for 2000 hours.

In addition, preferred coatings which were obtained using a coatingmaterial according to the invention show high resistance in analternating climate test, only slight cracking occurring in spite ofdeformation of the base body. The loading programme shown in FIG. 1 canpreferably be used for carrying out the alternating climate test (BMW PR303—part d).

Below, the present invention is to be explained with reference toexamples and comparative examples without any limitation being intendedthereby.

COMPARATIVE EXAMPLE 1

In a small-scale experiment, the efficiency of the present reactivemixtures was investigated. For this purpose, an injection moulding(200×100×3 mm) was first produced from a PMMA moulding material (8N,commercially available from Röhm GmbH) and preheated to 85° C. For thepreheating, the injection moulding was placed between two metalcylinders (having high gloss), the lower cylinder having a diameter of150 mm and the upper metal cylinder a diameter of 120 mm. In order toprevent excessive cooling of the upper metal cylinder, the latter, wastaken down after thermostating of the injection moulding for about 5minutes, placed alongside the hotplate and further heated (thermostatedat 85° C.). In the meantime, the injection moulding remained lying flaton the large metal cylinder and was further heated again for 5 minuteswithout weighting.

Thereafter (after thermostating of the injection moulding for 10minutes), 1.5 g of reactive mixture which comprised 68.60% by weight of1,6-hexanediol diacrylate, 29.40% by weight of trimethylolpropanetriacrylate, 1% by weight of bis(4-tert-butylcyclo-hexyl)peroxydicarbonate (thermal initiator) and 1% by weight of1-benzoylcyclohexanol (®Irgacure 184) was added to the injectionmoulding and the reaction solution was weighted (pressed) immediatelywith a small metal cylinder at 85° C. The coating was then allowed tocure for 60 sec, the reaction beginning about 15 seconds after the smallmetal cylinder had been placed on top. This could be measured on thebasis of emerging reaction solution. A crack-free coating was obtained.

The scratch resistance of the coating was investigated in a small-scaletest using steel wool, a scale of 0 (very high scratch resistance) to 7(very low scratch resistance) being used. The coating thus obtainedachieved a scratch resistance of 6 (low scratch resistance).

EXAMPLE 1

Comparative Example 1 was substantially repeated, but curing waseffected by UV irradiation after the thermal curing of the coatedinjection moulding. The coating remained free of cracks. The scratchresistance of the coating was investigated in a small-scale test usingsteel wool, the coating thus obtained achieving a scratch resistance of3 (good scratch resistance).

COMPARATIVE EXAMPLE 2

Comparative Example 1 was substantially repeated, but a reactive mixturewhich comprised 67.90% by weight of 1,6-hexanediol diacrylate, 29.10% byweight of trimethylolpropane triacrylate, 1% by weight ofbis(4-tert-butylcyclohexyl) peroxydicarbonate (thermal initiator) and 2%by weight of benzoylcyclohexanol (®Irgacure 184) was used.

The scratch resistance of the coating was investigated in a small-scaletest using steel wool, the coating thus obtained achieving a scratchresistance of 6 (low scratch resistance).

EXAMPLE 2

Comparative Example 2 was substantially repeated, but curing by UVirradiation was effected after the thermal curing of the coatedinjection moulding. The coating remained free of cracks. The scratchresistance of the coating was investigated in a small-scale test usingsteel wool, the coating thus obtained achieving a scratch resistance of3 (good scratch resistance).

EXAMPLE 3

Example 1 was substantially repeated, but a reactive mixture whichcomprised 97.75% by weight of trimethylolpropane triacrylate, 0.25% byweight of bis(4-tert-butylcyclohexyl) peroxydicarbonate (thermalinitiator) and 2% by weight of 1-benzoylcyclohexanol (®Irgacure 184) wasused.

The thermal curing reaction began after about 15 seconds. After the UVcuring, a crack-free coating which had a thickness of about 20 μm(average value of four individual measurements) was obtained.

The scratch resistance of the coating was investigated in a small-scaletest using steel wool, the coating thus obtained achieving a scratchresistance of 1 (very good scratch resistance).

EXAMPLE 4

Example 3 was substantially repeated, but the reaction temperature wasreduced from 85° C. to 80° C.

The thermal curing reaction began after about 25 seconds. After the UVcuring, a crack-free coating which had a thickness of about 25 μm(average value of four individual measurements) was obtained.

The scratch resistance of the coating was investigated in a small-scaletest using steel wool, the coating thus obtained achieving a scratchresistance of 1 (very good scratch resistance).

EXAMPLE 5

Example 4 was substantially repeated, but a reactive mixture whichcomprised 97.50% by weight of trimethylolpropane triacrylate, 0.50% byweight of bis(4-tert-butylcyclohexyl) peroxydicarbonate (thermalinitiator) and 2% by weight of 1-benzoylcyclohexanol (®Irgacure 184) wasused.

The thermal curing reaction began after about 15 seconds. After the UVcuring, a crack-free coating which had a thickness of about 12 μm(average value of four individual measurements) was obtained.

The scratch resistance of the coating was investigated in a small-scaletest using steel wool, the coating thus obtained having a scratchresistance of 1 (very good scratch resistance).

EXAMPLE 6

Example 4 was substantially repeated, but a reactive mixture whichcomprised 97.00% by weight of trimethylolpropane triacrylate, 1.00% byweight of bis(4-tert-butylcyclohexyl) peroxydicarbonate (thermalinitiator) and 2% by weight of 1-benzoylcyclohexanol (®Irgacure 184) wasused.

The thermal curing reaction began after about 8 seconds. After the UVcuring, a crack-free coating which had a thickness of about 13 μm(average value of four individual measurements) was obtained.

The scratch resistance of the coating was investigated in a small-scaletest using steel wool, the coating thus obtained having a scratchresistance of 1 (very good scratch resistance).

EXAMPLE 7

Example 4 was substantially repeated, but a reactive mixture whichcomprised 9 g of trimethylolpropane triacrylate, 1 g of pentaerythrityltetraacrylate, 0.05 g of bis(4-tert-butylcyclohexyl) peroxydicarbonate(thermal initiator) and 0.20 g of 1-benzoylcyclohexanol (®Irgacure 184)was used.

After the UV curing, a crack-free coating which had a thickness of about27 μm (average value of four individual measurements) was obtained.

The scratch resistance of the coating was investigated in a small-scaletest using steel wool, the coating thus obtained having a scratchresistance of about 0.5 (very good scratch resistance).

EXAMPLE 8

Example 7 was substantially repeated, but a reactive mixture whichcomprised 8 g of trimethylolpropane triacrylate, 2 g of pentaerythrityltetraacrylate, 0.05 g of bis(4-tert-butylcyclohexyl) peroxydicarbonate(thermal initiator) and 0.20 g of 1-benzoylcyclohexanol (®Irgacure 184)was used.

After the UV curing, a crack-free coating which had a thickness of about14 μm (average value of four individual measurements) was obtained.

The scratch resistance of the coating was investigated in a small-scaletest using steel wool, the coating thus obtained having a scratchresistance of about 0 (excellent scratch resistance; no scratches couldbe produced by muscle power).

EXAMPLE 9

Example 7 was substantially repeated, but a reactive mixture whichcomprised 5 g of trimethylolpropane triacrylate, 5 g of pentaerythrityltetraacrylate, 0.05 g of bis(4-tert-butylcyclohexyl) peroxydicarbonate(thermal initiator) and 0.20 g of 1-benzoylcyclohexanol (®Irgacure 184)was used.

After the UV curing, a crack-free coating which had a thickness of about16 μm (average value of four individual measurements) was obtained.

The scratch resistance of the coating was investigated in a small-scaletest using steel wool, the coating thus obtained having a scratchresistance of 0 (excellent scratch resistance; no scratches could beproduced by muscle power).

EXAMPLE 10

Example 7 was substantially repeated, but a reactive mixture whichcomprised 3 g of trimethylolpropane triacrylate, 7 g of pentaerythrityltetraacrylate, 0.025 g of bis(4-tert-butylcyclohexyl) peroxy-dicarbonate(thermal initiator) and 0.20 g of 1-benzoylcyclohexanol (®Irgacure 184)was used.

The thermal curing was effected at 85° C., a curing time of about 30seconds being sufficient. After the UV curing, a crack-free coating wasobtained.

The scratch resistance of the coating was investigated in a small-scaletest using steel wool, the coating thus obtained achieving a scratchresistance of 0 (excellent scratch resistance).

EXAMPLE 11

In a small-scale experiment, the efficiency of the present reactivemixtures was investigated. For this purpose, an injection moulding(200×100×3 mm) was first produced from a PMMA moulding material (8N,commercially available from Röhm GmbH) and preheated to 85° C. For thepreheating, the injection moulding was placed between two metalcylinders (having high gloss), the lower cylinder having a diameter of150 mm and the upper metal cylinder a diameter of 120 mm. In order toprevent excessive cooling of the upper metal cylinder, the latter, wastaken down after thermostating of the injection moulding for about 5minutes, placed alongside the hotplate and further heated (thermostatedat 85° C.). In the meantime, the injection moulding remained lying flaton the large metal cylinder and was further heated again for 5 minuteswithout weighting.

Thereafter (after thermostating the injection moulding for 10 minutes),1.5 g of a reactive mixture which comprised 5 g of trimethylolpropanetriacrylate, 5 g of pentaerythrityl tetraacrylate, 0.025 g ofbis(4-tert-butylcyclohexyl) peroxydicarbonate (thermal initiator) and0.20 g of 1-benzoylcyclohexanol (®Irgacure 184) was added to theinjection moulding and the reaction solution was immediately weighted(pressed) with a small metal cylinder at 85° C. and a metal blockweighing 3 kg. The coating was then allowed to cure for 30 seconds. Acrack-free coating was obtained.

After the thermal curing, the coated injection moulding was cured by UVirradiation. Here, the cooled coating was exposed to UV light for about1 minute without nitrogen. A crack-free, 20 μm thick coating wasobtained. The scratch resistance of the coating was investigated in asmall-scale test using steel wool, the coating thus obtained achieving ascratch resistance of 0 (excellent scratch resistance).

EXAMPLE 12

Example 11 was substantially repeated, but a layer thickness of 80 μmwas produced. For this purpose, the injection moulding was covered witha polyester film which had been cut out in annular form and had athickness of about 80 μm.

After the thermal curing, an initially crack-free coating was obtained.As a result of exposure to UV light, however, substantial crackingoccurred. The scratch resistance of the coating was investigated in asmall-scale test using steel wool, the coating thus obtained having ascratch resistance of 0 (excellent scratch resistance).

EXAMPLE 13

In a small-scale experiment, the efficiency of the present reactivemixtures was investigated. For this purpose, an injection moulding(200×100×3 mm) was first produced from a PMMA moulding material (8N,commercially available from Röhm GmbH) and preheated to 85° C. For thepreheating, the injection moulding was placed between two metal blocks(having high gloss), which had a size of 170·170·27 mm. In order toprevent excessive cooling of the upper metal block, the latter, wastaken down after thermostating of the injection moulding for about 5minutes, placed alongside the hotplate and further heated (thermostatedat 85° C.). In the meantime, the injection moulding remained lying flaton the lower metal block and was further heated again for 5 minuteswithout weighting.

Thereafter (after thermostating the injection moulding for 10 minutes),1.5 g of a reactive mixture which comprised 5 g of trimethylolpropanetriacrylate, 5 g of pentaerythrityl tetraacrylate, 0.05 g ofbis(4-tert-butylcyclohexyl) peroxydicarbonate (thermal initiator) and0.20 g of 1-benzoylcyclohexanol (®Irgacure 184) was added to theinjection moulding and the reaction solution was immediately pressedwith the upper metal block at 85° C. The coating was then allowed tocure for 60 seconds. A crack-free coating was obtained.

After the thermal curing, the coated injection moulding was cured by UVirradiation. Here, the cooled coating was exposed to UV light for about1 minute without nitrogen. A crack-free coating was obtained.

The scratch resistance of the coating was investigated by an abrasivedisc test according to ASTM 1044 (12/05) (applied weight 500 g, numberof cycles=100). The haze of the moulding increased to 2.8% thereby.Furthermore, the adhesive strength of the coating was determined bymeans of a cross hatch test. For this purpose, the coating was scoredcrosswise and thus divided into chessboard-like individual segments. Thespacing between the lines is about 1 mm here. An adhesive tape is thenstuck on and peeled off again. For carrying out the test, an adhesivetape which is available under the tradename Type 4104 from Tesa wasused. The adhesive strength of the coating was so high that noindividual segment was detached.

EXAMPLE 14

Example 13 was substantially repeated, but a reactive mixture whichcomprised 10 g of trimethylolpropane triacrylate, 0.05 g ofbis(4-tert-butylcyclohexyl) peroxydicarbonate (thermal initiator) and0.20 g of 1-benzoylcyclohexanol (®Irgacure 184) was used.

The scratch resistance of the coating was investigated by an abrasivedisc test according to ASTM 1044 (12/05) (applied weight 500 g, numberof cycles=100). The haze of the moulding increased to 5.4% thereby.Furthermore, the adhesive strength of the coating was determined bymeans of a cross hatch test. For this purpose, the coating was scoredcrosswise and thus divided into chessboard-like individual segments. Thespacing between the lines is about 1 mm here. An adhesive tape is thenstuck on and peeled off again. For carrying out the test, an adhesivetape which is available under the tradename Type 4104 from Tesa wasused. The adhesive strength of the coating was so high that noindividual segment was detached.

Furthermore, a moulding thus produced was subjected to an alternatingclimate test according to (BMW PR 303—part d), the loading programmebeing shown in FIG. 1. The moulding was greatly deformed by this test,but the coating showed only very slight cracking.

In addition, a moulding thus produced was irradiated with xenon arclight for 2000 hours (according to DIN EN ISO 4892, part 2, xenon arctester: Atlas/Heraeus type 1200), with the result that the transmittancedecreased only from 91.8% to 91.1%. The scratch resistance of thecoating was likewise slightly adversely affected by the xenon arc test.The haze of the moulding increased from 5.4% to 22.3%.

EXAMPLE 15

Example 13 was substantially repeated, but a reactive mixture whichcomprised 5 g of trimethylolpropane triacrylate, 5 g of 1,6-hexanedioldiacrylate, 0.05 g of bis(4-tert-butylcyclohexyl) peroxydicarbonate(thermal initiator) and 0.20 g of 1-benzoylcyclohexanol (®Irgacure 184)was used.

The scratch resistance of the coating was investigated by an abrasivedisc test according to ASTM 1044 (12/05) (applied weight 500 g, numberof cycles=100). The haze of the moulding increased to 5.8% thereby.Furthermore, the adhesive strength of the coating was determined bymeans of a cross hatch test. For this purpose, the coating was scoredcrosswise and thus divided into chessboard-like individual segments. Thespacing between the lines is about 1 mm here. An adhesive tape is thenstuck on and peeled off again. For carrying out the test, an adhesivetape which is available under the tradename Type 4104 from Tesa wasused. The adhesive strength of the coating was so high that noindividual segment was detached.

Furthermore, a moulding thus produced was subjected to an alternatingclimate test according to (BMW PR 303—part d), the loading programmebeing shown in FIG. 1. The moulding was greatly deformed by this test,but the coating showed no cracking.

In addition, a moulding thus produced was irradiated with xenon arclight for 2000 hours (according to DIN EN ISO 4892, part 2, xenon arctester: Atlas/Heraeus type 1200), with the result that the transmittancedecreased only from 91.4% to 91.1%. The scratch resistance of thecoating was likewise slightly adversely affected by the xenon arc test.The haze of the moulding increased from 5.8% to 13.5%.

EXAMPLE 16

Example 13 was substantially repeated, but a reactive mixture whichcomprised 7.2 g of trimethylolpropane triacrylate, 1.8 g of1,6-hexanediol diacrylate, 1.0 g of polysiloxane (lubricant; RC 725,commercially available from Goldschmidt GmbH), 0.1 g ofbis(4-tert-butylcyclohexyl) peroxydicarbonate (thermal initiator) and0.20 g of 1-benzoylcyclohexanol (®Irgacure 184) was used. In addition, aPMMA moulding material coloured black (8N black 90084, commerciallyavailable from Röhm GmbH) was used.

The thermal curing was effected at 90° C., a curing time of about 60seconds being sufficient. After the UV curing, a crack-free coating wasobtained.

The scratch resistance of the coating was investigated by an abrasivedisc test according to ASTM 1044 (12/05), (applied weight 500 g, numberof cycles=100). A decrease in the gloss at 20° according to DIN EN ISO2813 of 6.8% was obtained thereby.

EXAMPLE 17

Example 16 was substantially repeated, but the reaction temperature wasincreased from 90° C. to 95° C.

The scratch resistance of the coating was investigated by an abrasivedisc test according to ASTM 1044 (12/05) (applied weight 500 g, numberof cycles=100). A decrease in the gloss at 20° according to DIN EN ISO2813 of 5.3% was obtained thereby.

EXAMPLE 18

Example 15 was substantially repeated, but a reactive mixture whichcomprised 5 g of trimethylolpropane triacrylate, 5 g of 1,6-hexanedioldiacrylate, 0.1 g of bis(4-tert-butylcyclohexyl) peroxydicarbonate(thermal initiator) and 0.20 g of 1-benzoylcyclohexanol (®Irgacure 184)was used. In addition, a PMMA moulding material coloured black (8N black90084, commercially available from Röhm GmbH) was used.

The thermal curing was effected at 90° C., a curing time of about 30seconds being sufficient. After the UV curing, a crack-free coating wasobtained.

The scratch resistance of the coating was investigated by an abrasivedisc test according to ASTM 1044 (12/05) (applied weight 500 g, numberof cycles=100). A decrease in the gloss at 20° according to DIN EN ISO2813 of 4.7% was obtained thereby.

Furthermore, a moulding thus produced was subjected to an alternatingclimate test according to (BMW PR 303—part d), the loading programmebeing shown in FIG. 1. The moulding was greatly deformed by this test,but the coating showed no cracking.

EXAMPLE 19

Example 18 was substantially repeated, but a reactive mixture whichcomprised 7 g of trimethylolpropane triacrylate, 3 g of 1,6-hexanedioldiacrylate, 0.1 g of bis(4-tert-butylcyclohexyl) peroxydicarbonate(thermal initiator) and 0.20 g of 1-benzoylcyclohexanol (®Irgacure 184)was used.

The thermal curing was effected at 90° C., a curing time of about 60seconds being sufficient. After the UV curing, a crack-free coating wasobtained.

The scratch resistance of the coating was investigated by an abrasivedisc test according to ASTM 1044 (12/05) (applied weight 500 g, numberof cycles=100). A decrease in the gloss at 20° according to DIN EN ISO2813 of 1.8% was obtained thereby.

Furthermore, a moulding thus produced was subjected to an alternatingclimate test according to (BMW PR 303—part d), the loading programmebeing shown in FIG. 1. The moulding was greatly deformed by this test,but the coating showed no cracking.

1-17. (canceled)
 18. A process for the production of coated mouldings,the method comprising injecting a moulding material into an injectionmould and cooling to produce a moulding, wherein the injection mould ischanged so that a space forms between that surface of the moulding whichis to be coated and an inner surface of the injection mould, theresulting space is filled by injection moulding with a reactive mixtureaccording to comprising at least 40% by weight of (meth)acrylates havingat least two double bonds, at least one photoinitiator and at least onethermal initiator, and the reactive mixture is first thermally curedand, after the thermal curing, cured by irradiation.
 19. The processaccording to claim 18, wherein the moulding material comprises at leastone polymer selected from the group consisting of polymethylmethacrylate, polymethylmethacrylimide, styrene-acrylonitrile copolymer,styrene-maleic acid copolymer and polymethyl methacrylate copolymers.20. The process according to claim 19, wherein the moulding materialcomprises at least 50% by weight of polymethyl methacrylate, polymethylmethacrylimide and/or polymethyl methacrylate copolymers.
 21. Theprocess according to claim 18, wherein the thickness of the coating isin the range of 5 μm to 75 μm.
 22. The process according to claim 18,wherein the moulding material is injected into the injection mould at atemperature in the range of 220 to 330° C.
 23. The process according toclaim 18, wherein the moulding material is cooled to a temperature inthe range of 70 to 150° C. before the reactive mixture is injected intothe space.
 24. The process according to claim 18, wherein the reactivemixture is thermally cured at a temperature in the range of 80 to 130°C. in the injection mould.
 25. The process according to claim 18,wherein the thermally cured reactive mixture is cured by irradiation ata temperature in the range of 10 to 40° C.
 26. The process according toclaim 25, wherein the thermally cured reactive mixture is cured using UVradiation. 27-34. (canceled)
 35. The process according to claim 18,wherein the reactive mixture comprises at least 60% by weight of(meth)acrylates having at least two double bonds.
 36. The processaccording to claim 18, wherein the reactive mixture comprises at least90% by weight of (meth)acrylates having at least two double bonds. 37.The process according to claim 18, wherein the reactive mixturecomprises at least one (meth)acrylate having three or more double bonds.38. The process according to claim 37, wherein the proportion of(meth)acrylates having three or more double bonds is at least 25% byweight, based on the weight of the reactive mixture.
 39. The processaccording to claim 38, wherein the proportion of (meth)acrylates havingthree or more double bonds is at least 50% by weight, based on theweight of the reactive mixture.
 40. The process according to claim 18,wherein the reactive mixture comprises not more than 75% by weight ofmonomers having two or less double bonds.
 41. The process according toclaim 18, wherein the reactive mixture has a dynamic viscosity in therange of 1 to 200 mPa·s at 25° C.
 35. The process according to claim 18,wherein the reactive mixture comprises at least 60% by weight of(meth)acrylates having at least two double bonds.
 36. The processaccording to claim 18, wherein the reactive mixture comprises at least90% by weight of (meth)acrylates having at least two double bonds. 37.The process according to claim 18, wherein the reactive mixturecomprises at least one (meth)acrylate having three or more double bonds.38. The process according to claim 37, wherein the proportion of(meth)acrylates having three or more double bonds is at least 25% byweight, based on the weight of the reactive mixture.
 39. The processaccording to claim 38, wherein the proportion of (meth)acrylates havingthree or more double bonds is at least 50% by weight, based on theweight of the reactive mixture.
 40. The process according to claim 18,wherein the reactive mixture comprises not more than 75% by weight ofmonomers having two or less double bonds.
 41. The process according toclaim 18, wherein the reactive mixture has a dynamic viscosity in therange of 1 to 200 mPa·s at 25° C.
 42. The process according to claim 18,wherein the reactive mixture comprises 0.01% by weight to 3% by weightof photoinitiator, based on the weight of the reactive mixture.
 43. Theprocess according to claim 18, wherein the reactive mixture comprises0.03% by weight to 5% by weight of thermal initiator, based on theweight of the reactive mixture.
 44. The process according to claim 18,wherein the weight ratio of photoinitiator to thermal initiator is inthe range of 20:1 to 1:5.
 45. The process according to claim 18, whereinthe reactive mixture comprises 1,6-hexanediol diacrylate,trimethylolpropane triacrylate and/or pentaerythrityl tetraacrylate. 46.The process according to claim 45, wherein the reactive mixturecomprises trimethylolpropane triacrylate and 1,6-hexanediol diacrylate,the weight ratio of trimethylolpropane triacrylate to 1,6-hexanedioldiacrylate being in the range of 5:1 to 1:5.
 47. The process accordingto claim 45, wherein the reactive mixture comprises trimethylolpropanetriacrylate and pentaerythrityl tetraacrylate, the weight ratio oftrimethylolpropane triacrylate to pentaerythrityl tetraacrylate being inthe range of 5:1 to 1:5.
 48. The process according to claim 45, whereinthe reactive mixture comprises pentaerythrityl tetraacrylate and1,6-hexanediol diacrylate, the weight ratio of pentaerythrityltetraacrylate to 1,6-hexanediol diacrylate being in the range of 5:1 to1:5.
 49. The process according to claim 18, wherein the reactive mixturecomprises a lubricant.
 50. The process according to claim 18, whereinthe reactive mixture comprises colorants, metallic pigments, UVstabilizers, fillers or nanomaterials.